Most low frequency power limiting devices presently known in the state of the art are fabricated around a nonlinear element, generally a ferrite element or diode, in a coaxial or waveguide structure.
At millimeter wavelengths and submillimeter wavelengths, however, the techniques and components used in the microwave region are inapplicable due to the relatively high power losses and the high cost. For this reason, the state of the art has turned to employing a dielectric transmission medium located on a conductive ground plane which forms thereby an image guide transmission line structure. The dielectric transmission medium typically comprises a high resistivity material such as gallium arsenide (GaAs) which is adapted to propagate the signals through the submillimeter frequency region with relatively little loss.
In the above referenced related application entitled, "Millimeter Wave Signal Limiter", there is disclosed a power limiter comprised of a high resistivity dielectric transmission line located on a conductive ground plane and having a plurality of slots formed in the transmission line at predetermined spaced intervals with the slots each containing a small rectangular block of high anisotropic uniaxial barrium ferrite. A biasing DC magnetic field is transversely applied across the ferrite bodies by means of a pair of rare earth permanent magnets located at the sides of the dielectric transmission line and ground plane. The magnetic field applied to the ferrite bodies causes magnetic moments in the ferrite material to precess at a rate determined by the strength of the biasing magnetic field whereby, at a critical threshold level of power coupled to and propagating down the transmission line, spin waves are generated in the ferrite material to absorb signal energy and thus limit the power coupled out of the transmission line to the threshold level.
In the other related application entitled, "Monolithic Planar Doped Barrier Subharmonic Mixer", there is disclosed a monolithic signal mixer for millimeter wave and submillimeter wave signals and employing a semiconductor planar doped barrier diode structure formed on a dielectric (GaAs) transmission line and being of the type shown in disclosed in U.S. Pat. No. 4,410,902, entitled, "Planar Doped Barrier Semiconductor Device", which issued to Roger J. Malik, on Oct. 18, 1983. Disclosed in the Malik patent is a device fabricated in GaAs which comprises a n+-i-p+-i-n+ structure wherein an extremely narrow p+ planar region is positioned between adjoining regions of intrinsic semiconductor material.
Accordingly, it is an object of the present invention to provide an improvement in millimeter wave devices.
It is another object of the invention to provide a millimeter wave device in the form of a power limiter.
It is a further object of the invention to provide a monolithic planar doped barrier power limiter which operates at millimeter wave and submillimeter wave frequencies.
It is yet another object of the invention to provide a passive millimeter wave power limiter for the front end section of a millimeter wave signal receiver.